Advances in the mechanical, electrical, and controls arts are bringing robots and similar mechanical devices closer to achieving physical tasks traditionally performed by humans. As such, many of these robots require articulated joints to complete these tasks. For example, some state-of-the-art legged robots walk with bipedal movement to traverse from one point to another. Many of these articulated joints employ joint-mounted motors to articulate the articulated joint. Such joint-mounted motors simplify controls for the articulated joint, but result in joint assemblies that are heavy and bulky.
A cable-driven joint is known to reduce the weight and size on these articulated joints. Rather than mounting the motor on the joint, the motor is mounted to a main body of the robot. Accordingly, non-stretchable cables extend from the body-mounted motor to the articulated joint assembly so that the joint may articulate as desired. While body-mounted motors successfully reduce the weight of the articulated joint, the cable-driven joint is more difficult to control because non-stretchable cables generally require an additional motor for each joint. Thus, the overall weight, cost, and complexity of the robot tend to increase for cable-driven joints.
Furthermore, both the joint-mounted drive unit and the non-stretchable cable-driven drive unit create rigidity in the articulated joint not present in biological joints, such as human joints. This rigidity leaves the articulated joint susceptible to forces and impacts that create imbalance and stress in the robot and increases energy consumption in order to overcome the impact. More particularly, energy consumption is increased, because the energy cannot be effectively absorbed and transferred into kinetic energy while propelling the body forward. This is in stark contrast to a biological joint that is capable of absorbing and transferring kinetic energy for this purpose. Thus, joint-mounted and non-stretchable cable motorized drive units for use with mechanical articulating joints are presently less capable than the biological counterpart.
There is a need for a motorized drive system and method for articulating a mechanical joint, such as the mechanical joint of a robot, that addresses present challenges and characteristics such as those discussed above.